[ticket/12789] Remove the directories in \phpbb\cache\driver\memory::purge()

PHPBB3-12789
[ticket/12789] Move duplicated functions to the base class

PHPBB3-12789
Merge remote-tracking branch 'github-nicofuma/ticket/12789' into develop-ascraeus

* github-nicofuma/ticket/12789:
  [ticket/12789] Move duplicated functions to the base class
  [ticket/12789] Remove the directories in \phpbb\cache\driver\memory::purge()
[ticket/12738] Pass $this->config in content_visibility constructor

PHPBB3-12738
Merge pull request #2838 from dhruvgoel92/ticket/12738

[ticket/12738] Pass $this->config in content_visibility constructor

* dhruvgoel92/ticket/12738:
  [ticket/12738] Pass $this->config in content_visibility constructor